The development of shrimp aquaculture, in spite of its global necessity, is largely at stake as significant ecological and pathological problems are increasing in the vast majority of the shrimp producing countries. Shrimp immunology is a key element in establishing strategies for controlling diseases in shrimp aquaculture. The total haemocyte count (THC), differential haemocyte count (DHC), total plasma protein (TPP), Phagocytic activity (PA), bacterial clearance efficiency (BCE) and bactericidal activity (BE) were examined when the F. indicus shrimps (11.32±1.20 g) were immersed in seawater (39 ppt and 25 ± 1 ^○C) containing hot-water extracts of brown alga Sargassum glaucescens at 100, 300 and 500 mg/l. These parameters increased significantly (p < 0.05) when the shrimp were immersed in seawater containing hot-water extracts at 100 mg/l after 3h and 300 and 500 mg/l after 2 h. F. indicus shrimps that were immersed in hot-water extracts at 300 and 500 mg/l had increased phagocytic activity and clearance efficiency to Vibrio spp. after 2 hours. But bactericidal activity increased significantly after 1 hour in the same concentrations.